How to enlarge a hole in a porcelain sink??
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  1. #1
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    Default How to enlarge a hole in a porcelain sink??

    A friend is restoring a vintage house and needs to enlarge the holes in a cast iron sink without damaging the porcelain.

    Must be done in-situ. The sink can't be removed without great difficulty/expense.

    He needs to do the same with the bathtub.

    Any suggestions? TIA

    - Leigh

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    Default Re: How to enlarge a hole in a porcelain sink??


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    Quote Originally Posted by emccarthy View Post
    The saw will need to be piloted.
    Perhaps careful work with a dremel?

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    Leigh, the enamel is going to chip unless you go abrasive like emccarthy suggests. I'd think about using abrasive to grind the enamel back from the hole (cover bare spot later with the tap or drain flange) then grind the cast iron (keeping everything cool/without vibration). A small hand held grinder dremel type grinder might work though slow. The best bet for your friend would be to get new faucets and/or drain that would fit or make/find and adapter if he can.

    Dave

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    I've used stacked holesaws on a long thread arbor for this (the smaller one as a pilot for the existing hole). My experience is that there is some porcelain chipping, which must be painted for rust protection. However, the chipping is usually covered by the flange of whatever (faucet, vent, etc.) that goes on top.

    The abrasive type holesaws do have less problem with chipping, but enamel paint to touch up the cast iron and prevent rust from spreading under the porcelain is still needed.

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    Thanks for all the comments. I'll pass them on.

    Any others?

    - Leigh

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    Several times in granite I have taken a hole saw and drilled thru plywood to create a guide for the hole saw. Then center the plywood over the hole to enlarge and go for it... This eliminates the need for arbors.

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    We used to use diamond hole saws for drilling large pottery (vase fountains) and of course they had no pilot so the solution was to drill a hole through a scrap of lumber with the bit and then center the hole in the wood over your mark as a drill bushing and drill away. Once you get the bit started just a little bit you can do away with the wood and finish the hole. Steady stream of liquid coolant (water) helps keep things cool and makes the process faster. Hope that helps!

    Too slow - Lazz beat me to the punch!

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    Sintered diamond drills, grinding burrs, and hole saws are available. Use with a bit of water to keep cool. Pretty simple to make a stepped guide plug to fit existing holes if needed for a center-guided hole saw.

    ~TW~

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    Find someone with a machine shop to make or modify a brass drain to fit the existing hole.

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    Upon further thought...
    I came to the same conclusion.
    Use wood for the pilot and drill it with a abrasive hole saw.

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    I had a similar problem with a antique sink that was all porcelain, I just machined a new drain part out of brass and silver soldered it to a modern size one, then had it nickel plated. I have often wondered many years down the road some plumber is going to try to get a new one and take it to the plumbing shop and ask if they have one of these?

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    Quote Originally Posted by The real Leigh View Post
    Thanks for all the comments. I'll pass them on.

    Any others?

    - Leigh
    Yep. BTDTGTTS. Source or modify fittings to match existing holes, use large bezels if need be.

    Supply lines don't NEED large passage, modern drains CAN be slicker than older cast-brass or iron ones, so will clear cleanly enough with what may be considered undersize by present US practice. Travel '2 star' (or lesser..) Italian Pensiones and see such everywhere that 'JFW'.

    Bill

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    You want a continuous-rim diamond drill for that - those segmented tooth ones in the link are too coarse and will hammer the enamel away in big chunks. A close-fitting timber guide is a must.

    Sharpen the drill before use (and periodically if it blunts whilst drilling the iron) by drilling a few shallow holes in a soft cinder block. Use water.

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    If I'm thinking of this right (HA) cast iron with porcelain coating? Emccarthy idea +1 could cut a plywood plug for existing hole (tight fit), to serve as a guide for the pilot. Use something akin to silly putty to dam up around the cutting area to hold water for lube, cooling and chip removal. If the porcelain is coating cast Fe and the sink bottom is flat you might consider a mag drill. As far as chipping just go slow and deal with what shakes out. Personally I would try and get an old cheap sink of same the construction to give a few trials on. Just for my info how much material has to be removed? This could really change the approach.

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    I once used a diamond drum to modify a sink. Fits on a 5/8 right angle grinder. It was about 1" dia. Or try these. https://www.regentstoneproducts.com/...e=SHAFTRTRTOOL

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    How much does the hole need to be enlarged? Dremels have a shitty plastic coupling inside that readily breaks. I'm in the re machine the brass part camp. Grinding the porcelain can only lead to future corrosion,paint or not.

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    Are you cutting it larger because it is an odd old size? If you could find that odd old size or an adapter would you go that way instead?
    I have an old tub and I found a google search to come up with the parts I need to hook it all up.
    Joe

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    A granite countertop installer has the right diamond bits to make this an easy project - or you can go to Contractors Direct - Concrete Saw, Wet Saw, Tile Cutter, Cement Mixers to find diamond core bits.

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    Abrasive slurry with a clay dam. Thin walled brass tubing, have a pilot

    go through the hard stuff and then a smaller hole saw.

    Silicon carbide grit maybe


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